The invention relates to an automatic nut feeding device used in a manufacturing line for automobiles or the like.
Automatic feeding devices for nuts such as pierce nuts, caulking nuts, weld nuts or the like are provided with a body for temporarily holding a nut, which is passed through a nut feeding hole via a chute by means of pneumatic pressure or the like to be successively fed into the body while laterally sliding. FIG. 4 is a cross sectional view showing a general construction of such a device, and the reference numeral 1 designates a body, 2 a nut feeding hole formed on one side of the body, 3 a vertical hole, through which a punch (not shown) for striking a nut N passes, and 4 an opening and closing member for temporarily holding a nut N until striking. A nut N fed to an interior of the body 1 from the nut feeding hole 2 is temporarily held on the opening and closing member 4, and when a punch descends through the vertical hole 3, the opening and closing member 4 is simultaneously opened to permit the nut N to be struck into a mating member.
In the case where the nut N is not correctly fed to the interior of the body 1 for some reasons, however, the punch when being made to descend performs lost striking to cause various troubles. Conventionally, a sensor pin 5 for detecting a nut N is mounted on a side opposite to the nut feeding hole 2 in the body 1 as shown in FIG. 4.
The sensor pin 5 is metallic and provided with a lead wire 6 for electrically detecting contact of the nut N as shown in the figure. The sensor pin 5 is insulated at its periphery by a covering tube 7 of rubber, and is fixed in the body 1 by means of a bonding agent 8 after being positioned so as to be capable of detecting that the nut N has been correctly fed. Also, a surface of the sensor pin for contact with the nut N is fixed by the bonding agent 8 and then finished by means of electric spark machining.
Because the sensor pin 5 gets a shock repeatedly each time the nut N abuts against the pin, however, the sensor pin 5 is slightly shifted in position after use over a long term, and so there is the possibility that a nut N cannot be correctly detected when such shift becomes great. Such trouble will give rise to stoppage of a manufacturing line to cause a heavy damage.
Also, there has been involved a problem that since the sensor pin 5 is insulated at its periphery by the covering tube 7 of rubber, it is not easy even for a new sensor pin to be mounted correctly in a position where it contacts with a nut N fed at a predetermined position and it is difficult to repairingly correct a position of the sensor pin 5, which is displaced in position during use. Further, manufacturing cost is high since the sensor pin 5 is finished by means of electric spark machining after being fixed by the bonding agent 8.
The invention solves the above-mentioned problems of the prior device and provides an automatic nut feeding device, in which failure in detection is not caused even after use over a long term, mounting of a sensor is easy, and manufacturing cost can be reduced relative to the prior device.
To solve the above-mentioned problems, the automatic nut feeding device of the invention has a feature in comprising a body provided on a side surface thereof with a nut feeding hole, and a spring plunger type conduction sensor mounted on a side of the body opposite to the nut feeding hole therein and adapted to be pushed by a nut, which is passed through the nut feeding hole to be fed into the body while laterally sliding. In addition, the automatic nut feeding device of the invention may further comprise a spring-retainer type sensor pin provided on a front surface of the spring plunger type conduction sensor and adapted to be pushed by a nut as fed.
The automatic nut feeding device of the invention is constructed such that a spring plunger type conduction sensor is mounted in an interior of a body by means of a screw, so that even when repeatedly given a shock, a spring absorbs the shock and so the sensor is free of positional displacement. Also, the device can correctly detect a nut even when the sensor is mounted with rough positional accuracy, and the device is easy to repair and can be reduced in manufacturing cost.
In addition, it is possible to use the disclosure of EP 0 703 037 A1 of the present applicant as an apparatus for successively supplying nuts to the body and striking the same into a member, into which nuts are to be struck. Therefore, European Patent Publication No. EP 0 703 037 A1, the disclosure of which is herein incorporated by reference, discloses an apparatus for continuously feeding and driving nuts, in which nuts are arranged so as to be made postures thereof to be vertically right, and a predetermined number of nuts are intermittently transported and provided through a nut feeding hole to be fed into a body of this specification while laterally sliding.